The principal focus of this project is to establish the molecular basis of the processes that regulate cell membrane assembly. Our emphasis has presently been on mechanisms of membrane lipid bilayer assembly. Using total membrane lipids of E. coli, B. stearothermophilis, and human red blood cells, we have identified a process of lipid bilayer assembly in aqueous dispersions of these lipids that fulfills several important requirements of bilayer assembly in cell membranes: a) the process yields unilamellar bilayers, b) the bilayers form spontaneously from lipids that are avilable in the metabolic pool at the growth temperature of the cell, and c) the dependence of the temperature of membrane formation on the fatty acid composition of the membrane lipids resembles the way lipid composition changes with growth temperature in bacteria. Methods for studying the influence of electrolyte, proteins and pharmacological agents on the lipid bilayer assembly process have been developed utilizing quasielastic light scattering techniques.